The present invention relates to a suspension for disc drive incorporated in an information processing apparatus, such as a personal computer, and a manufacturing method therefor.
A hard disc drive (HDD) for recording on or retrieving information from a rotating magnetic disc or magneto-optical disc includes a carriage that can turn around a shaft. The carriage is turned around the shaft by means of a positioning motor.
As described in U.S. Pat. No. 4,167,765, for example, the carriage is provided with an arm, a suspension on the distal end portion of the arm, a head portion including a slider attached to the suspension, etc. When the slider is slightly lifted from the disc as the disc rotates at high speed, an air bearing is formed between the disc and the slider.
The suspension comprises a load beam formed of a precision thin plate spring, a flexure formed of a very thin plate spring that is fixed to the distal end portion of the load beam by laser welding or the like, and a base plate fixed to the proximal portion of the beam by laser welding or the like. The base plate is fixed to a suspension mounting surface of the arm.
In modern disc drives of this type, the density of information to be recorded tends to be enhanced, and the disc rotation has an inclination to higher speed. Accordingly, the suspensions for disc drive require a good vibration characteristic such that they can be positioned highly accurately with respect to the recording surface of discs. Further, the suspensions should not be easily influenced by air turbulence that is caused by high-speed rotation of the discs. To meet the demand for various new functions, moreover, the suspensions of this type also tend to be subjected to more complicated machining.
As the density of information to be stored in each disc increases, the suspensions are expected to have high stiffness and a low spring constant. FIG. 14 shows one such conventional suspension 1, which comprises a load beam 2 that integrally includes a rigid body portion 2a of length L1 and a spring portion 2b of length L2. Conventionally, therefore, the necessary performance (high stiffness) for the rigid body portion 2a and the performance (low spring constant) required by the spring portion 2b cannot be secured at the same time.
The material and thickness of the whole rigid body portion 2a, in particular, are inevitably restricted by the required properties of the spring portion 2b. In order to enhance the stiffness of the body portion 2a, therefore, it is necessary to form bent edges 3 by bending the opposite side edges of the rigid body portion 2a or to form ribs 4 by embossing. Accordingly, the load beam 2 must be subjected to high-accurately machining, thus entailing a lot of processes for machining, and therefore, high costs.
The bent edges 3 or ribs 4 on the load beam 2 may hinder a flow of air. When a disc rotates at high speed, therefore, the load beam 2 is easily influenced by air turbulence and flutters. A base plate 5 is fixed to the proximal portion of the load beam 2. Further, a flexure 6 is fixed to the distal end portion of the load beam 2. The flexure 6 is fitted with a slider 8 that constitutes a head portion 7.
In a load beam described in Jpn. Pat. Appln. KOKAI Publication No. 9-191004, for example, the thickness of a spring portion is partially reduced by partial etching in order to lower the spring constant of the load beam. Since the thickness of the spring portion cannot be accurately controlled by partial etching, however, it is unstable, so that the spring constant is liable to variation.
In the case of the suspension described in Jpn. Pat. Appln. KOKAI Publication No. 9-128919, a plurality of narrow plate spring portions are formed around a slider mounting portion of a load beam by etching or pressing. The plate spring portions are deformed in the thickness direction. In this prior art example, the plate spring portions should be formed in a narrow region on the distal end of the load beam. Therefore, the load beam requires very delicate machining, so that its shape and spring constant are liable to variation and its quality is unstable.